The present invention generally relates to apparatus for cooling electronic components included in a portable computer, such as a laptop, notebook, subnotebook and the like and, more particularly, to a two-tier cooling apparatus for such a computer.
Over recent years there has been widespread development of personal computers, with a dramatic increase in the design, development and sale of computers which are portable. These portable computers are not significantly larger than small portable typewriters, and contain their own built-in central processing unit, memory, hard drive, disk drives, keyboard, display and carrying handle. The keyboard usually projects forwardly from a base and the display is typically a liquid crystal display contained on one side of a panel or lid which folds down flat on the upper surface of the keyboard to serve as a cover to protect the keyboard and display during storage and travel.
Laptop computers typically utilize the newest generation of integrated circuits which often operate at sufficiently high frequencies that they generate more heat than can be dissipated by conventional heat sinks or the like. Increases in heat generation have often been accommodated by simply increasing the quantity or size of these heat dissipation elements. However, the relatively small size of a portable, laptop computing device complicates heat dissipation by limiting airflow, crowding heat generating components, and reducing the space available for heat dissipation devices. As a consequence, portable computing devices today utilize systems that cannot easily be cooled by natural convection or by forced air cooling systems.
One area of laptop computers that has been exploited for dissipating heat is the back of the display portion of the case. This area has not been used effectively to dissipate heat in many prior art laptops because it was difficult to convey heat to this area from the processor region of the laptop without passing through some type of hinge structure forming a connection between the lower housing of the laptop and the display panel. While at a first view this appears to be an obvious way to transfer heat from the main body of a laptop computer through the hinge and to the area behind the display, this is not a straightforward or simple task. The geometry and heat transfer capacity of a conventional hinge are not suitable for transferring heat between the base and display of a portable computing device. The main difficulty in transferring heat between the base and the display through a conventional hinge is that many efficient heat conductors, e.g., heat pipes, thermal loops, cold plates, are not capable of sustaining the repetitive motion expected between the hinged base and display without becoming brittle due to stress fatigue. Since a heat pipe is a solid hermetically sealed unit, it does not readily lend itself to any mechanical motion of one end while the other end remains fixed, as would be the case if a heat pipe were passed directly through the hinge of a portable computer. In order to produce a reliable product with a heat pipe based thermal management scheme, it must be implemented so as to minimize any bending stresses in the material in order to minimize the possibility of failure.
There have been many prior art solutions to the problem of transferring heat from the main body of a laptop computer, through a hinge mechanism, to the area behind the display screen. For example, U.S. Pat. No. 5,880,929, issued to Bhatia discloses a heat exchanger system for use in a hinged computing device. The hinged computing device includes a base housing connected to a display housing by one or more hinges. A number of heat generating electronic components are located within the base housing, and a display screen is positioned in the display housing. The heat exchanger system includes a heat pipe located in the base and thermally coupled to both an electronic component and the hinge to allow heat transfer from the electronic component to the hinge. A flat plate heat pipe located in the display housing is mechanically and thermally coupled to the hinge to allow heat transfer from the hinge to the flat plate heat pipe for dissipation through the display housing.
U.S. Pat. No. 6,122,166, issued to Mochizuki et al., discloses a device for cooling a personal computer that includes a body having a heat generating electronic element and a keyboard section connected in an openable manner to the personal computer body through a hinge. A first heat pipe, which has one end portion connected to the electronic element in a heat transferring manner, and a second heat pipe, which has one end portion arranged along an electromagnetic insulating plate mounted in the keyboard section, are connected through the hinge so as to rotate relative to each other.
U.S. Pat. No. 6,253,836, issued to Mitchell discloses a notebook computer having a base housing with a heat-generating microprocessor and a lid housing pivotally connected to the base housing. Operating heat from the microprocessor is transferred to the lid housing, via a specially designed thermosyphoning heat pipe structure formed from first and second heat pipes. The first heat pipe has a rectangular cross-section, an evaporating portion arranged in thermal communication with the microprocessor, and a coiled condensing portion centered about the lid hinge line and having a circularly cross-sectioned interior side surface defined by flat sides of the first heat pipe. The second heat pipe has a circular cross-section, an evaporating portion pivotally received within the coiled first heat pipe portion, and a condensing portion arranged in thermal communication with the lid housing. When the lid housing is opened and closed, the evaporating portion of the second heat pipe is rotated within the coiled first heat pipe portion and slidably engages its circularly cross-sectioned interior side portion.
U.S. Pat. No. 6,288,896, issued to Hsu discloses a heat dissipation system for use in hinged computing devices. The device includes a thermally conductive joint having first and second receptacles which are generally parallel to one another. A first heat pipe is at least partially disposed within the first receptacle, and is adapted to be thermally coupled to a heat source within the hinged computing device. A second heat pipe is at least partially disposed within the second receptacle, and is adapted to be thermally coupled to a heat sink. The thermally conductive joint permits the transfer of heat from the first heat pipe to the second heat pipe to transfer heat from the heat source to the heat sink portion of the hinged computing device.
U.S. Pat. No. 6,449,149, issued to Ohashi et al., discloses a cooling system for a laptop computer, where the computer includes a first casing on which are mounted a keyboard and a wiring board and a second casing which is rotatably mounted on the first casing with a hinge. The cooling structure of the laptop computer includes one or more elements that are the subject of cooling arranged within the first casing, a first heat-discharging member thermally connected with this element and the first casing, a second heat-discharging member that is arranged in the interior of the second casing, and an interconnection between them for thermally connecting the first heat-discharging element and the second heat-discharging element.
The present invention provides a cooling system for a hinged portable computing device having a housing including first and second portions, and a heat generating component carried in the first housing portion. A first passive heat transfer device is carried within the first housing portion, and includes a first end thermally coupled to the heat generating component and a second end. A second passive heat transfer device is carried within the second housing portion, and includes a first end thermally coupled to the second housing portion and a second end. A hinge structure interconnects the first and second housing portions for pivotal movement relative to one another, where the hinge structure includes a heat conductive first gudgeon having a pintle and a thermal interface block. The thermal interface block is disposed in the second housing portion and connected in thermal communication with the second first passive heat transfer device. A heat conductive second gudgeon is also provided having a journal and a thermal interface block. The thermal interface block of the second gudgeon is connected in thermal communication with the first passive heat transfer device, and the pintle is rotatably received within the journal so as to be in heat exchange relationship with the second gudgeon, thereby forming an integral portion of the hinge structure.